Method for repairing fuel nozzle guides for gas turbine engine combustors using cold metal transfer weld technology

ABSTRACT

A fuel nozzle guide for a combustor of a turbine engine includes an annular base with a hub section, the hub section at least partially formed of a Cold Metal Transfer (CMT) weld and a method and system therefor.

BACKGROUND

The present disclosure relates to a gas turbine engine and, moreparticularly, to a weld repair therefor.

Gas turbine engines, such as those powering modern commercial andmilitary aircraft, include a compressor for pressurizing an airflow, acombustor for burning a hydrocarbon fuel in the presence of thepressurized air, and a turbine for extracting energy from the resultantcombustion gases. The combustor generally includes radially spaced innerand outer liners that define an annular combustion chamber therebetween.Arrays of circumferentially distributed combustion air holes penetratemultiple axial locations along each liner to radially admit thepressurized air into the combustion chamber. A plurality ofcircumferentially distributed fuel nozzles project into a forwardsection of the combustion chamber through a respective fuel nozzle guideto supply the fuel to be mixed with the pressurized air.

Combustor components may require repair. Oftentimes, the repair isperformed with gas tungsten arc welding, plasma arc welding and laserwelding.

SUMMARY

A fuel nozzle guide for a combustor of a turbine engine according to anexemplary aspect of the present disclosure includes an annular base witha hub section, the hub section at least partially formed of a Cold MetalTransfer (CMT) weld.

A weld system according to an exemplary aspect of the present disclosureincludes a fixture which supports a Cold Metal Transfer (CMT) weld torchand a rotary table which rotates relative to the Cold Metal Transfer(CMT) weld torch.

A method of repairing a fuel nozzle guide for a combustor of a turbineengine according to an exemplary aspect of the present disclosureincludes removing a portion of a hub section that extends from anannular base of the fuel nozzle guide. Building up a lip of the hubsection with a Cold Metal Transfer (CMT) weld to form a weld builduplip. Machining the weld buildup lip to a desired original predetermineddimension.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a schematic cross-section of a gas turbine engine;

FIG. 2 is a perspective partial sectional view of an exemplary annularcombustor that may be used with the gas turbine engine shown in FIG. 1;

FIG. 3 is an exploded view of a forward assembly of the exemplarycombustor with a fuel nozzle guide;

FIG. 4 is a method of repair for the fuel nozzle guide;

FIG. 5 is a perspective view of the fuel nozzle guide after a lipremoval step;

FIG. 6 is a perspective view of the fuel nozzle guide after a CMT weldbuildup step;

FIG. 7 is a schematic view of a weld system for use with the method ofrepair;

FIG. 8 is a perspective view of the fuel nozzle guide after a machiningstep;

FIG. 9 is a schematic view of a workpiece holder which defines a heightspecific to a particular fuel nozzle guide for use with the method ofrepair; and

FIG. 10 is a schematic view of another workpiece holder which defines aheight specific to another particular fuel nozzle guide for use with themethod of repair.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flowpath whilethe compressor section 24 drives air along a core flowpath forcompression and communication into the combustor section 26 thenexpansion through the turbine section 28. Although depicted as aturbofan gas turbine engine in the disclosed non-limiting embodiment, itshould be understood that the concepts described herein are not limitedto use with turbofans as the teachings may be applied to other types ofturbine engines.

The engine 20 generally includes a low speed spool 30 and a high speedspool 32 mounted for rotation about an engine central longitudinal axisA relative to an engine static structure 36 via several bearing systems38. It should be understood that various bearing systems 38 at variouslocations may alternatively or additionally be provided.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 and a low pressureturbine 46. The inner shaft 40 is connected to the fan 42 through ageared architecture 48 to drive the fan 42 at a lower speed than the lowspeed spool 30. The high speed spool 32 includes an outer shaft 50 thatinterconnects a high pressure compressor 52 and high pressure turbine54. A combustor 56 is arranged between the high pressure compressor 52and the high pressure turbine 54. The inner shaft 40 and the outer shaft50 are concentric and rotate about the engine central longitudinal axisA which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel within thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The turbines 54, 46 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion.

With reference to FIG. 2, the combustor 56 generally includes an outercombustor liner 60 and an inner combustor liner 62. The outer combustorliner 60 and the inner combustor liner 62 are spaced inward from acombustor case 64 such that a combustion chamber 66 is defined therebetween. The combustion chamber 66 is generally annular in shape and isdefined between combustor liners 60, 62.

The outer combustor liner 60 and the combustor case 64 define an outerannular plenum 76 and the inner combustor liner 62 and the combustorcase 64 define an inner annular plenum 78. It should be understood thatalthough a particular combustor is illustrated, other combustor typeswith various combustor liner panel arrangements will also benefitherefrom. It should be further understood that the disclosed coolingflow paths are but an illustrated embodiment and should not be limitedonly thereto.

The combustor liners 60, 62 contain the flame for direction toward theturbine section 28. Each combustor liner 60, 62 generally includes asupport shell 68, 70 which supports one or more liner panels 72, 74mounted to a hot side of the respective support shell 68, 70. The linerpanels 72, 74 define a liner panel array which may be generally annularin shape. Each of the liner panels 72, 74 may be generally rectilinearand manufactured of, for example, a nickel based super alloy or ceramicmaterial.

The combustor 56 further includes a forward assembly 80 immediatelydownstream of the compressor section 24 to receive compressed airflowtherefrom. The forward assembly 80 generally includes an annular hood82, a bulkhead assembly 84, a multiple of fuel nozzles 86 (one shown)and a multiple of fuel nozzle guides 90 (one shown) that defines acentral opening 92. The annular hood 82 extends radially between, and issecured to, the forwardmost ends of the liners 60, 62. The annular hood82 includes a multiple of circumferentially distributed hood ports 94that accommodate the respective fuel nozzle 86 and introduce air intothe forward end of the combustion chamber 66. Each fuel nozzle 86 may besecured to the outer case 64 and projects through one of the hood ports94 and through the central opening 92 within the respective fuel nozzleguide 90.

Each of the fuel nozzle guides 90 is circumferentially aligned with oneof the hood ports 94 to project through the bulkhead assembly 84. Eachbulkhead assembly 84 includes a bulkhead support shell 96 secured to theliners 60, 62, and a multiple of circumferentially distributed bulkheadheatshields segments 98 secured to the bulkhead support shell 96 aroundthe central opening 92.

The forward assembly 80 introduces primary core combustion air into theforward end of the combustion chamber 66 while the remainder enters theouter annular plenum 76 and the inner annular plenum 78. The multiple offuel nozzles 86 and surrounding structure generate a swirling,intimately blended fuel-air mixture that supports combustion in theforward section of the combustion chamber 66.

With reference to FIG. 3, each of the fuel nozzle guides 90 has agenerally annular base 100 with an outwardly or downstream extendingfrusto-conical hub section 102 that forms the central opening 92dimensioned for a snug slip-fit mounting of the fuel nozzle 86. Thecenterline of the fuel nozzle 86 is concurrent with the centerline F ofthe fuel nozzle guide 90.

The fuel nozzle guide 90 is typically a cast metal component subject tohigh wear due to exposure to the combustion chamber 66 and maintenanceof the fuel nozzle 86. Typically, a lip 104 of the hub section 102becomes highly worn such that a Cold Metal Transfer (CMT) weldtechnology is utilized with a semi automatic weld cycle to restore thelip 104 to original dimensions by the method disclosed herein (FIG. 4).

With Reference to FIG. 4, step 200 of a manufacture or repair for thefuel nozzle guide 90 includes machining of the lip 104 to remove adesired amount of material and provide a weld ready surface W (FIG. 5).It should be understood that various geometries may be provided by theweld ready surface W and such surface may be flat or featured tofacilitate a weld interface.

Step 202 of the repair includes a weld cycle via Cold Metal Transfer(CMT) weld technology with an automated or robot-assisted torch T tobuild up the lip 104 (FIG. 6). Cold Metal Transfer (CMT) weld technologyis based on short circuiting transfer, or in other words, on adeliberate, systematic discontinuing of the arc. Results are a sort ofalternating “hot-cold-hot-cold” sequence. The “hot-cold” methodsignificantly reduces the arc pressure. A wide process window and thehigh stability thereof define one Cold Metal Transfer (CMT) process. Theweld wire material may be, for example, of a Hastelloy X, Stellite 31 orother aerospace grade weld material, such as nickel cobalt superalloyweld fillers. It should be understood that the weld material may beequivalent to the base material or may alternatively be a softermaterial than the base material. Every time short circuiting occurs, thecontrol interrupts the power supply and controls the retraction of theweld wire. This motion takes place at a rate of up to, for example,about seventy (70) times per second. The weld wire retraction motionfacilitates droplet detachment during the short circuit. The reducedthermal input also offers advantages such as low distortion and highprecision.

The fuel nozzle guide 90 is rotated by a weld system 110 (FIG. 7) thatalso maintains the torch T in a stationary position and orientation asfurther described below. In the disclosed non-limiting embodiment, theCMT weld buildup height defines a height of about 0.080″ (20 mm-21 mm)in a continuous weld to define a single start and a single stop with atotal weld time of approximately 111 seconds. It should be understoodthat various weld buildup heights may alternatively or additionally beprovided based on the component and or repair required.

In step 204, the weld may be finished through a machining operation toreturn the lip 104 of the hub section 102 to a desired originalpredetermined dimensional geometry (FIG. 8). It should be understoodthat additional finishing operations may alternatively or additionallybe performed.

With reference to FIG. 7, the weld system 110 general includes a fixture112 which supports the torch T in a desired position and orientationrelative to a rotary table 114 or “rotab.” The fixture 112 includes atorch holder 116 that is readily adjusted through a rack and pinion, or,other arrangement to locate the torch T in a fixed position relative tothe rotary table 114 and thereby relative to the fuel nozzle guide 90 orworkpiece to be repaired. That is, the torch T is mechanically fixedalong the Z-axis and thus into a desired position relative the fuelnozzle guide 90.

The torch T in the disclosed non-limiting embodiment is oriented toprovide between a perpendicular to about a ten (10) degree push or trailorientation relative to the fuel nozzle guide 90. It should be notedthat other orientations may be used to maximize weld efficiency. Itshould also be noted that a computing device C (illustratedschematically) can be used to implement various functionality, such asoperation of the torch T and rotation of the rotary table 114. In termsof hardware architecture, such a computing device can include aprocessor, memory, and one or more input and/or output (I/O) deviceinterface(s) that are communicatively coupled via a local interface asgenerally understood.

The rotary table 114 may include a workpiece holder 118 that defines aworking height H along the Z axis specific to each particular fuelnozzle guide 90. That is, one thick workpiece holder 118A is utilizedfor a relatively small fuel nozzle guide 90A (FIG. 9) while another thinworkpiece holder 118B is utilized for a relatively large or thick fuelnozzle guide 90B (FIG. 10). Either holder may be mounted to the rotarytable 114. Such specific workpiece holders permit a single heightsetting for the fixture 112 to be utilized with various workpieces so asto facilitate high throughput operations. Each workpiece holder 118A,118B may also include a unique attachment interface 120A, 120B to assuremistake proof installation to the rotary table 114.

It should be understood that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like arewith reference to the normal operational attitude of the vehicle andshould not be considered otherwise limiting.

It should be understood that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent disclosure.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

What is claimed is:
 1. A method of repairing a fuel nozzle guide for acombustor of a turbine engine comprising: removing a portion of a hubsection which extends from an annular base of the fuel nozzle guide;building up a lip of the hub section with a Cold Metal Transfer (CMT)weld as a continuous weld with a single start and a single stop to forma weld buildup lip; and machining the weld buildup lip to a desiredoriginal predetermined dimension.
 2. The method as recited in claim 1,further comprising: rotating the fuel nozzle guide.
 3. The method asrecited in claim 2, wherein the rotating step is performed with respectto a stationary weld torch.
 4. The method as recited in claim 1, furthercomprising: maintaining a torch which forms the Cold Metal Transfer(CMT) weld stationary.
 5. The method as recited in claim 1, furthercomprising building up the weld buildup lip to define a height of about0.080″ (20 mm-21 mm).
 6. The method as recited in claim 1, wherein theremoving step results in a weld ready surface.
 7. The method as recitedin claim 6, wherein the weld surface includes at least one feature tofacilitate a weld interface.
 8. The method as recited in claim 1,wherein the building up step is accomplished with a nickel cobaltsuperalloy weld wire.
 9. The method as recited in claim 1, wherein thebuilding up step is accomplished with a weld wire of the same materialas the fuel nozzle guide.
 10. The method as recited in claim 1, whereinthe building up step is accomplished with a weld wire of a materialdifferent than a material of the fuel nozzle guide, and wherein thematerial of the weld wire is softer than the material of the fuel nozzleguide.
 11. The method as recited in claim 1, wherein the building upstep is accomplished by a systematic discontinuing of a weld arc. 12.The method as recited in claim 11, wherein the systematic discontinuingof the arc is at a rate of less than about 70 times per second.
 13. Themethod as recited in claim 1, wherein the fuel nozzle guide is a castmetal component.
 14. The method as recited in claim 1, wherein the hubsection is frusto-conical.